It is known especially in the commercial vehicle sector that automated group transmissions are used, which usually consist of a main transmission with an upstream group and/or a downstream group. Preferably, the upstream group is a splitter group which doubles the number of gears of the main transmission. Preferably the downstream group is a range group which provides a larger transmission ratio spread and thus, for example in the case of a two-stage range group in the form of a planetary gear system, can again double the number of gears. For some time it has been sought in such cases to enable the gears in the individual parts of the transmission and also over the transmission as a whole to be shifted with as little traction force interruption as possible or, if possible, to engage the gears without traction force interruption.
Automated group transmissions can also be used in combination with hybrid drive technology. Here too, gear engagement as free from traction force interruption as possible is preferred. For example, from the document DE 10 2009 054 752 A1 by the present applicant such a combination is known. In a drive-train of a motor vehicle with a hybrid drive, namely an internal combustion engine and an electric machine, and an automated group transmission, the electric machine of the hybrid drive is connected to the, or each countershaft. In this way, when a shift is carried out in the splitter group of the group transmission traction force support can be provided. However, only powershifts (supporting gear shifts) for shifts in the splitter group are possible. If the coupling or decoupling of the electric machine and the countershafts are to be shiftable, this is enabled by an additional shifting element which is not needed for the function of the mechanical gearset.
To minimize the fuel consumption, drive-trains for motor vehicles are often designed such that most of the driving takes place in the direct transmission gear. In the direct transmission gear the force flow is produced by a direct coupling of the drive input shaft to the drive output shaft, which results in greater efficiency. From the document DE 102 39 396 A1 by the present applicant a transmission is known, in which when the direct gear is engaged the parts of the transmission which in the direct gear are not involved in the force flow, are wholly or partially decoupled. In that way frictional losses in those parts of the transmission can be prevented and the efficiency of the transmission is improved. However, in that case no powershifts are possible.